Imaging lens, optical apparatus and method for forming image using this imaging lens

Abstract

An imaging lens includes a first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power, which are disposed in order from an object. The first lens group has a first lens component having a negative refractive power and a second lens component having a positive refractive power, which are disposed in order from the object, and conditions expressed by the expressions 0.12<f/f 1 <0.47 and 0.016<D 12 /f<0.079 are satisfied, when f 1 is a focal length of the first lens group, f is a focal length of the imaging lens, and D 12 is an air distance between the first lens component and the second lens component of the first lens group.

1. An imaging lens, comprising a first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power, which are disposed in order from an object,
 the first lens group including a plurality of lenses, 
 the second lens group including a cemented lens of a negative lens component having a concave surface facing the object and a positive lens component having a convex surface facing the image, and a biconvex positive lens component, which are disposed in order from the object, and 
 a condition expressed by the following expression being satisfied:
   3.0 <TL/Y max<4.0 
 
 where TL is a total length of the imaging lens, and Ymax is a maximum image height. 
 
     
     
       2. The imaging lens according to  claim 1 , wherein the second lens group comprises a cemented lens of a negative meniscus lens having a concave surface facing the object and a positive meniscus lens having a convex surface facing the image, and a biconvex positive lens, which are disposed in order from the object. 
     
     
       3. The imaging lens according to  claim 1 , wherein the first lens group comprises the first lens component made of a negative meniscus lens having a convex surface facing the object, and the second lens component made of a positive meniscus lens having a convex surface facing the object, which are disposed in order from the object. 
     
     
       4. The imaging lens according to  claim 1 , wherein a condition expressed by the following expression is satisfied:
     nd 1>1.65 
 where nd 1  is a refractive index of the first lens component of the first lens group on the d-line. 
 
     
     
       5. The imaging lens according to  claim 1 , wherein a condition expressed by the following expression is satisfied:
   3.8<( r 2 F+r 1 R )/( r 2 F−r 1 R )<11.8 
 where r 1 R is a radius of curvature of an image side lens surface of the first lens component, and r 2 F is a radius of curvature of an object side lens surface of the second lens component. 
 
     
     
       6. The imaging lens according to  claim 1 , wherein the second lens group comprises a biconvex positive lens, and the biconvex positive lens includes at least one aspherical surface. 
     
     
       7. The imaging lens according to  claim 1 , wherein a condition expressed by the following expression is satisfied:
   0.13 <f 2 /f 1<0.47 
 where f 1  is a focal length of the first lens group, and f 2  is a focal length of the second lens group. 
 
     
     
       8. The imaging lens according to  claim 1 , wherein the focus on a close object is adjusted by moving the second lens group toward the object. 
     
     
       9. The imaging lens according to  claim 1 , wherein the second lens group includes at least one aspherical surface. 
     
     
       10. An optical apparatus, comprising an imaging lens that forms an image of an object on a predetermined image surface, wherein the imaging lens is the imaging lens according to  claim 1 . 
     
     
       11. The imaging lens according to  claim 1 , wherein the first lens group including a negative lens component and a positive lens component, which are disposed in order from the object,
 the second lens group including a cemented lens of a negative lens component and a first positive lens component, and a second positive lens component, which are disposed in order from the object, and 
 conditions expressed by the following expressions being satisfied:
     nd 5<1.67 
     νd 5>50.0 
 
 where nd 5  is a refractive index of the second positive lens component of the second lens group on the d-line, and νd 5  is an Abbe number of the second positive lens component of the second lens group on the d-line. 
 
     
     
       12. The imaging lens according to  claim 11 , wherein a condition expressed by the following expression is satisfied:
   −0.30<( r 5 R+r 5 F )/( r 5 R−r 5 F )<0.40
 
 where r 5 F is a radius of curvature of an object side lens surface of the second positive lens component of the second lens group, and r 5 R is a radius of curvature of an image side lens surface of the second positive lens component of the second lens group. 
 
     
     
       13. The imaging lens according to  claim 11 , wherein a condition represented by the following expression is satisfied:
   0.60 <f/f 5<0.90 
 where f is a focal length of the imaging lens, and f 5  is a focal length of the second positive lens component of the second lens group. 
 
     
     
       14. The imaging lens according to  claim 11 , wherein the negative lens component of the first lens group includes at least one aspherical surface. 
     
     
       15. The imaging lens according to  claim 1 , wherein a condition expressed by of the following expression is satisfied:
   1.7 <TL/Σd< 2.2 
 where TL is a total length of the imaging lens, and Σd is a length on the optical axis, from a lens surface closest to the object in the first lens group to a lens surface closest to the image in the second lens group. 
 
     
     
       16. The imaging lens according to  claim 15 , wherein the first lens group including a first lens component having a negative refractive power and a second lens component having a positive refractive power, which are disposed in order from the object, and
 conditions expressed by the following expressions being satisfied:
   0.12 <f/f 1<0.47 
   0.016 <D 12 /f< 0.079 
 
 where f 1  is a focal length of the first lens group, f is a focal length of an imaging lens, and D 12  is an air distance between the first lens component and the second lens component of the first lens group. 
 
     
     
       17. The imaging lens according to  claim 15 , wherein the second lens group further including a cemented lens of a negative lens component having a concave surface facing the object and a positive lens component having a convex surface facing the image, and a biconvex positive lens component, which are disposed in order from the object, and
 all or a part of the second lens group being able to be shifted in a direction substantially perpendicular to the optical axis as a shift lens group. 
 
     
     
       18. The imaging lens according to  claim 17 , wherein a condition expressed by the following expression is satisfied:
   0.80 <f/fS< 1.10 
 where f is a focal length of the imaging lens, and fS is a focal length of the shift lens group. 
 
     
     
       19. A method for manufacturing an imaging lens, comprising the steps of:
 assembling a first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power in a lens barrel in order from an object; 
 configuring the first lens group by disposing a plurality of lenses when the step of assembling is performed; and 
 configuring the second lens group by disposing a cemented lens of a negative lens component having a concave surface facing the object and a positive lens component having a convex surface facing the image, and a biconvex positive lens component, in order from the object when the step of assembling is performed, 
 a condition expressed by the following expression being satisfied:
   3.0 <TL/Y max<4.0 
 
 where TL is a total length of the imaging lens, and Ymax is a maximum image height. 
 
     
     
       20. The method for manufacturing the imaging lens according to  claim 19 , wherein the second lens group comprises a cemented lens of a negative meniscus lens having a concave surface facing the object and a positive meniscus lens having a convex surface facing the image, and a biconvex positive lens, which are disposed in order from the object. 
     
     
       21. The method for manufacturing the imaging lens according to  claim 19 , wherein the first lens group comprises the first lens component made of a negative meniscus lens having a convex surface facing the object, and the second lens component made of a positive meniscus lens having a convex surface facing the object, which are disposed in order from the object. 
     
     
       22. The method for manufacturing the imaging lens according to  claim 19 , wherein a condition expressed by the following expression is satisfied:
     nd 1>1.65 
 where nd 1  is a refractive index of the first lens component of the first lens group on the d-line. 
 
     
     
       23. The method for manufacturing the imaging lens according to  claim 19 , wherein a condition expressed by the following expression is satisfied:
   3.8<( r 2 F+r 1 R )/( r 2 F−r 1 R )<11.8 
 where r 1 R is a radius of curvature of an image side lens surface of the first lens component, and r 2 F is a radius of curvature of an object side lens surface of the second lens component. 
 
     
     
       24. The method for manufacturing the imaging lens according to  claim 19 , wherein the second lens group comprises a biconvex positive lens, wherein the biconvex positive lens includes at least one aspherical surface. 
     
     
       25. The method for manufacturing the imaging lens according to  claim 19 , wherein a condition expressed by the following expression is satisfied:
   0.13 <f 2 /f 1<0.47 
 where f 1  is a focal length of the first lens group, and f 2  is a focal length of the second lens group. 
 
     
     
       26. The method for manufacturing the imaging lens according to  claim 19 , wherein the focus on a close object is adjusted by moving the second lens group toward the object. 
     
     
       27. The method for manufacturing the imaging lens according to  claim 19 , wherein the second lens group includes at least one aspherical surface. 
     
     
       28. The method for manufacturing an imaging lens according to  claim 19 , wherein configuring the first lens group by disposing a negative lens component and a positive lens component in order from the object when the step of assembling is performed; and
 configuring the second lens group by disposing a cemented lens of a negative lens component and a first positive lens component, and a second positive lens component in order from the object when the step of assembling is performed, 
 conditions expressed by the following expressions being satisfied:
     nd 5<1.67 
     νd 5>50.0 
 
 where nd 5  is a refractive index of the second positive lens component of the second lens group on the d-line, and νd 5  is an Abbe number of the second positive lens of the second lens group on to the d-line. 
 
     
     
       29. The method for manufacturing the imaging lens according to  claim 28 , wherein a condition expressed by the following expression is satisfied:
   −0.30<( r 5 R+r 5 F )/( r 5 R−r 5 F )<0.40
 
 where r 5 F is a radius of curvature of an object side lens surface of the second positive lens component of the second lens group, and r 5 R is a radius of curvature of an image side lens surface of the second positive lens component of the second lens group. 
 
     
     
       30. The method for manufacturing the imaging lens according to  claim 28 , wherein a condition expressed by the following expression is satisfied:
   0.60 <f/f 5<0.90 
 where f is a focal length of the imaging lens, and f 5  is a focal length of the second positive lens component of the second lens group. 
 
     
     
       31. The method for manufacturing the imaging lens according to  claim 28 , wherein the negative lens component of the first lens group includes at least one aspherical surface. 
     
     
       32. The method for manufacturing the imaging lens according to  claim 19 , wherein a condition expressed by the following expression is satisfied:
   1.7 <TL/Σd< 2.2 
 where TL is a total length of the imaging lens, and Σd is a length on the optical axis, from a lens surface closest to the object in the first lens group to a lens surface closest to the image in the second lens group. 
 
     
     
       33. The method for manufacturing an imaging lens according to  claim 32 , wherein configuring the first lens group by disposing a first lens component having a negative refractive power and a second lens component having a positive refractive power in order from the object when the step of assembling is performed,
 conditions expressed by the following expressions being satisfied:
   0.12 <f/f 1<0.47 
   0.016 <D 12 /f< 0.079 
 
 where f 1  is a focal length of the first lens group, f is a focal length of an imaging lens, and D 12  is an air distance between the first lens component and the second lens component of the first lens group. 
 
     
     
       34. The method for manufacturing an imaging lens according to  claim 32 , wherein configuring the second lens group by disposing a cemented lens of a negative lens component having a concave surface facing the object and a positive lens component having a convex surface facing the image, and a biconvex positive lens component in order from the object when the step of assembling is performed; and
 assembling all or a part of the second lens group as a shift lens group to be shifted in a direction substantially perpendicular to the optical. 
 
     
     
       35. The method for manufacturing the imaging lens according to  claim 34 , wherein a condition expressed by the following expression is satisfied:
   0.80 <f/fS< 1.10 
 where f is a focal length of the imaging lens, and fS is a focal length of the shift lens group.